This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ebola virus VP35 is a multifunctional protein significant to VP35 virulence and human mortality. It is a part of the viral RNA polymerase complex;also it is responsible for the RNA silencing, suppression and RNA-depended protein kinase inhibition. VP35 is composed of N-terminal coiled-coil region and C-terminal interferon inhibitory domain, which binds dsRNA. Two crystal structures of the C-terminal part of the protein were released in the last two years, with and without bound 8-bp dsRNA. It was found that this domain is monomeric when it is RNA free or else crystallizes as a dimer of dimers when bound to dsRNA. Even though several in vitro as well as in vivo biochemical studies were performed to elucidate the oligomerization states of this protein, there is no structural information on the full length EV VP35. Biochemical methods suggested the existence of at least four oligomeric forms of VP35 (monomer to tetramer, and trimer/tetramer), with some of them responsible for the virulence of the EV. Our goal is to make inquiry into the oligomerization properties of the full length EV VP35 by using pulse dipolar ESR and to follow on to infer its structure with the distance measurements on a set of single and double mutants.